Electrostatic precipitator



July 31, 1956 1.. M. ROBERTS ELECTROSTATIC PRECIPITATOR Filed Oct. 26,1954 INVENTOR LAWRENCE M. ROBERTS ATTORNEY United States Patent2,756,839 ELECTRGSTATIC PRECIPITATOR Lawrence M. Roberts, Bound Brook,N. 1., assignor to Research Corporation, New York, N. Y., a corporationof New York Application October 26, 1954, Serial No. 464,790

4'Claims. c1. 183-7) This invention relates to apparatus for separatingsuspended particulate material from gas streams, and in parti'cular toimproved liquid flush type electrostatic precipitators particularlyadapted for separating inflammable material or material or a corrosivenature from a stream of gas.

In the precipitation of certain acid gases, fluorine compounds and thelike which are particularly corrosive it is desirable to constructpreeipitator shells and interior structura'l members of wood to reducethe cost of the initial installation and to reduce corrosion by the acidgases and the fluorine compounds. On such installations it is thegeneral practice to employ water sprays or films of water tcremove theprecipitated material, to condition the gases and to keep the woodenportions of the precipitator soaked; This form of equipment has alsobeen used in electrostatic precipitators for collecting inflammablematerial, such as carbon. These Systems have generally proved to besatisfactory as long as there is a continuous fiow of water to theliquid flush or spray systems of the precipitator. However, upon thefailure or accidental cutting off ofthe water supply to theelectrostatic preci'pfl tator while the electrodes continue to beenergized, the wood portions of the precipitator or the inflammablematerial precipitated from the gas stream is very likely to burn as soonas the water has evaporated therefrom.

In the caseof fire in a wood type electrostatic precipr ta'tor completeloss of the installation often results. In the case of non-inflammabletype precipitator's' collecting inflammable material, the burningmaterial often causes back corona discharges thus interfering'with theefficient precipitator action and such fires often result in the formation of clinkers in the precipitator hopper 'cloggingthe' dust removalsystem. I

It is therefore a primary object of the present invention to providecontrol means interconnecting liquid flush or spray systems ofelectrostatic precipitators of wood type construction or thosecollecting inflammable material, and the high voltage energizingsystem'for the complementary electrodes whereby the precipitator isdeenergizedupon the failure or accidental or intentional cutting oif ofthe source of spray or flushing liquid.

It is af'urthcr object of the invention to provide such a device that isdependable in' operation, relatively ineX- pensive to construct, andefficient in operation.

A further object of the invention is to provide such a system whereinthe control means may be positioned in the liquid spray conduits orexternally thereof in the field of the spray coverage. 7

These and other objects and advantages are provided by the control meansfor a liquid'flu'sh'type electrostatic pr'c'ipitator which generallycomprises a shell having a dirty gas inlet and a clean gas outlet,complementary collecting and discharge electrodes supported within suchshell between the gas inlet and gas outlet, a source of high voltageelectricity for energizing said electrodes, a liquid spray system forsaid electrodes connected to a source of spray liquid, and control meansinterconnecting said liquid "ice spray means and said source of highvoltage electricity for dee'n'ergizing the complementary electrodes uponfailure of the liquid spray system.

7 The invention will be more particularly described with reference totheaccompanying drawings wherein:

Fig. 1 is a diagrammatic View of an electrostatic precipitator havingliquid spray means and an energizing system for the electrodes includingthe control means of the present invention;

Fig. 2 is an enlarged fragmentary view of one form of the control meansof the present invention; V

Fig. 3 is an enlarged fragmentary view of another form or the controlmeans of the present invention; and

I Fig. 4 is an enlarged fragmentary view of still another form of thecontrol means of the present invention.

Referring to' the drawings and in particular to Fig. l, 10" is the shellor casing of an electrostatic precipitatoi' having a gas inlet 12 and agas outlet 14. The shell of the precipitator may be constructed of woodfor use in the collection of certain acid gases, and fluorine compoundswhere it is desirable to use wood in the construction of the shell as ithas high resistance to corrosion and is relatively inexpensive. V d

Supported, within the flow pass of the gas through the precipitatorshell, are a plurality of collecting electrodes generally designated 16.In the drawings the electrodes are shown as a plurality of tubularextended surface col lecting pipes supported in a header sheet 18connected to the sides of the precipitator casing. Vertically suspendedwithin each of the tubular collecting electrodes 16 is a line wiredischarge electrode 20. The lower ends of the discharge electrodes areprovided with tensioning weights 22 and a steadying frame work generallyindicated 24 which is insulatedly supported from the side walls of theprecipitator casing.

The upper ends of the discharge electrodes 20 are connected to a bus bar26 to which high voltage electrical cur} rent is connected throughconduit 38 as is well known in the art.

The foregoing structural elements of the electrostatic precipitator havebeen shown by way of example only, and it is apparent that other wellknown forms of collect ing and discharge electrodes may be employed withthe control system of the present invention.

The energization system for the complementary discharge and collectingelectrodes generally comprises a source of alternating current 28connected to a high ten sion transformer 30 through a magnetic switch 32tobe more fully described hereinafter. Thesecondary 34 of thetransformer 30 is connected to a rectifier 3 6 and hence to: thedischarge and collecting electrodes through electrical conduits 38 and40. I v

The magnetic switch 32 generally comprises main contact members 42holding contact member 44, starting but} tor-146, and solenoid 48 foractuating main and holding contact members 42'and 44. The solenoid 48'is energized from a source of alternating current 50 through electricalconduits 52, 54, 54 and switch 56.

The electrostatic precipitator is also provided with one or more wateror other liquid supply mains 58 and a plurality of liquid spray heads 60to supply flushing liquid to the discharge and collecting electrodes,for conditioning the gas stream to be treated in the pre'cipitator', andfor protecting the side walls of the precipitator shell on installationswhere such shell is constructed of inflammable material. v I I Means"generally designated 62, sensitive to the flew of flushing liquid areprovided for actuating the switch 56 which controls the magnetic switch32. The control means 62 which is sensitive to the how of flushingliquid to the electrostatic precipitator may take various forms as shownin detail in Figures 2 through 4.

. through the main 53.

I? In Figure 2 of the drawings the control means 62 includes adifferential pressure control diaphragm 64 connected to the switch 56.The diaphragm 64- is contained in a housing 66 having a pair of ducts 63and 70 connected to the water main 58 at one end and at the other end tothe housing 66 on opposite sides of the diaphragm 64. The diaphragm 64and the control switch 56 are so arranged that when fluid is flowingthrough the main 58 to spray devices 60 the switch is in the closedposition as shown in the drawings. However, as soon as the flow ofliquid through main 58 is interrupted the pressure on either side of thediaphragm 64 is effected and the contacts of switch 56 open deenergizingthe solenoid 48, opening the main contacts 42 of the precipitatorenergizing control switch 32, which cuts ofi the flow of high voltageelectricity to the complementary discharge and collecting electrodes ofthe precipitator.

In Figure 3 of the drawings another form of control device 62 is shownwhich is operated by the flow of fluid In this form of the invention apivotally mounted control member 72 has a portion 74 projecting into themain 58 and an external portion 76 which makes contact with the switch56. As long as flushing liquid is flowing in the main 5% in thedirection of the arrows contact is made between element 76 and thecontacts of the lines 52 and 54. When the flow of liquid in main 58stops or is reduced a predetermined amount, the portion 76 of lever 72moves away from the switch 56 whereby the solenoid 48 is deenergized.

In Figure 4 of the drawings another form of the control means 62 isshown. In this form of the invention switch 56 is not directly actuatedby the How of flushing liquid in the main 58 but by means of a mercurywet bulb thermometer 80 connected to a relay 82. When the bulb 80 of thethermometer is wetted by the liquid issuing from the sprays 60 in theswitch 56 remains in the on position. However, as soon as the bulb 80becomes dry the mercury column within the thermometer moves out andrelay 82 opens the switch 56 controlling the flow of current to thesolenoid 48. In the form of the invention shown in Figure 4 a pluralityof wet bulb type thermometers 80 may be employed in the precipitatorwherein one or more relays 32 may be connected in parallel and thegroups of parallel connected relays may be further connected in serieswhereby the precipitator is deenergized only upon failure of more thanone of the spray devices 60.

It is also evident that the fluid flow control means shown in Figures 2and 3 may be connected to subrnains each controlling a battery of spraydevices whereby the precipitator is deenergized only upon failure of,for example, more than one of the batteries of spray devices.

From the foregoing description it will be seen that the control meansfor liquid flush type electrostatic precipitators fully accomplishes theaims, objects and advantages of the invention. It will also be apparentthat the embodiments shown are only exemplary particular forms ofapparatus for carrying out the present invention and that variousmodifications can be made in the construction and arrangement of theelements within the scope of the invention as defined in the appendedclaims.

I claim:

1. Control means for a liquid flush type electrostatic precipitatorcomprising a shell having a dirty gas inlet and a clean gas outlet,complementary collecting and discharge electrodes supported within saidshell between the gas inlet and gas outlet, a source of high voltageelectricity for energizing said electrodes, a liquid spray system forsaid electrodes connected to a source of spray liquid and control meansinterconnecting said liquid spray system and said source of high voltageelectricity for deenergizing the complementary electrodes upon failureof said liquid spray system.

2. Control means for a liquid flush type electrostatic precipitatorcomprising a shell having a dirty gas inlet and a clean gas outlet,complementary collecting and discharge electrodes supported within saidshell between the gas inlet and gas outlet, a source of high voltageelectricity for energizing said electrodes, a liquid spray system forsaid electrodes connected to a source of spray liquid including aconduit connecting such source to spray outlets, control meansinterconnecting said liquid spray system with said source of highvoltage electricity for deenergizing the complementary electrodes onfailure of said liquid spray system, said control means including asolenoid actuated switch between the source of high voltage electricityand the complementary discharge and collecting electrodes, a diaphragmtype differential pressure indicator in the conduit supplying flushingliquid to the liquid spray system, and switch means actuated by saidpressure indicator for energizing and deenergizing said solenoid switch.

3. Control means for a liquid flush type electrostatic precipitatorcomprising a shell having a dirty gas inlet and a clean gas outlet,complementary collecting and discharge electrodes supported within saidshell between the gas inlet and gas outlet, a source of high voltageelectricity for energizing said electrodes, a liquid spray system forsaid electrodes connected to a source of spray liquid including at leastone spray head positioned to direct flushing liquid to the complementarydischarge and collecting electrodes, a solenoid actuated switch betweensuch source of high voltage electricity and the complementary dischargeand collecting electrodes, control means interconnecting said liquidspray system and said source of high voltage electricity fordeenergizing the complementary electrodes upon failure of said liquidspray system, said control means including a wet bulb thermometerpositioned within the precipitator shell within the field of said sprayhead, a relay connected to said wet bulb thermometer and means actuatedby said relay for energizing and deenergizing said solenoid switchmeans.

4. Control means for a liquid flush type electrostatic precipitatorcomprising a shell having a dirty gas inlet and a clean gas outlet,complementary collecting and discharge electrodes supported within saidshell between the gas inlet and gas outlet, a source of high voltageelectricity for energizing said electrodes, a liquid spray system forsaid electrodes connected to a source of spray liquid including aconduit connecting such source to spray outlets, control meansinterconnecting said liquid spray system with said source of highvoltage electricity for deenergizing the complementary electrodes onfailure of said liquid spray system, said control means including asolenoid actuated switch between the source of high voltage electricityand the complementary discharge and collecting electrodes, a pivotallymounted control member, one end of said control member projecting intothe liquid flow path within said conduit, and switch means actuated bythe other end of said control means for energizing and deenergizing saidsolenoid switch.

References Cited in the file of this patent UNITED STATES PATENTS1,947,447 Brassert Feb. 20, 1934 FOREIGN PATENTS 568 Great Britain June11, 1889

